Yrare low-spin positive-parity states in N = 88 66 154 Dy

Abstract

Low-spin positive-parity yrare states of 66 154 Dy88 were established using the 155Gd(3He,4n) reaction at a beam energy of $E_{lab} = 37.5$ MeV. The AFRODITE spectrometer array at iThemba LABS was used to record $\gamma\gamma$ coincidences and measure DCO ratios and polarisation asymmetries. The $K^{\pi}=2^{+}$ $ \gamma$ band has been observed up to spin $13^{+}$ in the odd spins and to $ 12^{+}$ in the even spins. The staggering parameter S(I) of the $ \gamma$ band is compared to that found in other N = 88 isotones. Different behaviour of S(I) with increasing spin is observed for each of the isotones. We conjecture that the variation in S(I) is mainly due to mixing of the even-spin states with the same spin and parity states in neighbouring rotational bands. A second $ K^{\pi}=2^{+}$ band has been established up to a spin of $ 12^{+}$ in the even spins. We suggest that this is a $ \gamma$ band based on the $ J^{\pi} = 0^{+}$ state at $ E_{x} = 660.6$ keV.